Boating Between the Hawaiian Islands: What to Know

One of the best reasons to own a boat in Hawaii is sitting right there on the horizon: another island. Molokai's west end, Lanai's back side, a weekend in Lahaina. Yes, you can absolutely take your own boat between the islands — people do it every week. But Hawaii's channels are open-ocean crossings with a serious reputation, and the boat, the weather window, and the preparation all have to be right. Here's the straight version.

The channels: short distances, big water

The gaps between islands look small on a map. The water in them doesn't play small. The Kaiwi Channel (also called the Molokai Channel) between Oahu and Molokai is roughly 26 miles across and over 2,000 feet deep — and it's regarded as one of the toughest stretches of regularly-crossed ocean in the world. Oahu to Kauai is on the order of a hundred miles of open Pacific. Oahu to the Big Island is farther still.

What makes Hawaii's channels different is the funnel effect. Typical trade winds blow 12–18 knots across the state, but when that airflow squeezes between two islands it accelerates — channel winds can run 15 knots or more above the surrounding breeze, stacking steep wind waves on top of ocean swell. The Alenuihaha Channel between Maui and the Big Island is the most notorious of all, where gusts of 40–50 knots are a regular event. There's a reason interisland races and paddle crossings here are considered world-championship tests.

When to go

The crossing is won or lost before you leave the dock. A few local rules of thumb:

• Wait for a real weather window. Light or moderating trades, no frontal systems, manageable swell. If NOAA has a Small Craft Advisory up for the channel, the answer is no — full stop.
• Leave early. Trades typically build through the afternoon. Local boats leave Oahu at first light and are tied up — Lono Harbor, Kaunakakai, or beyond — before the wind fills in.
• Mind the direction. Oahu to Molokai or Maui is generally an upwind, up-swell run; the ride home is usually the fast, friendly leg. Plan fuel and patience for the hard direction.
• File a float plan. Tell someone where you're going, your route, and when you'll check in. Cell coverage mid-channel is not guaranteed.

The right boat for channel work

This is where buying decisions get real. A boat that's perfect inside the reef or trolling the Waianae coast is not automatically a channel boat. What experienced interisland skippers look for:

• A proven offshore hull. Deep-V center consoles and offshore powerboats in good condition, power catamarans (which ride channel chop notably better than comparable monohulls), or blue-water cruising sailboats.
• Reliable power — ideally redundant. Twin engines, or a meticulously maintained single with a plan B. Mid-channel is a bad place for deferred maintenance to come due.
• Fuel range with a fat reserve. The old rule of thirds: a third out, a third back, a third in reserve. Headwinds and sea state can push real-world burn far above the brochure number.
• Self-draining cockpit, solid bilge pumps, and honest safety gear — VHF, EPIRB or PLB, life jackets actually worn in the channel, and a life raft for the longer runs.

How long does the crossing take?

Depends entirely on the boat and the day. A powerboat cruising in the high teens to low twenties can put Oahu–Molokai behind it in under two hours in fair conditions; a displacement sailboat beating into the trades can spend most of a day on the same water. Longer runs — Oahu to Kauai, Maui to the Big Island — are genuine passages that deserve passage-level planning, and many cruisers break the trip into legs with anchorages or harbor stops along the way.

Paperwork and harbors on the other side

There's no customs or permit to move between islands — it's all Hawaii. But moorage on the neighbor islands is just as tight as on Oahu, so check ahead on transient slip or anchorage options at your destination, and confirm current harbor rules and fees with the Division of Boating and Ocean Recreation (DOBOR) before you commit to a plan that depends on a slip being open.

Hawaii Yacht Group is Oahu's boat & yacht brokerage, based in Honolulu. Questions about offshore-capable boats? Email contact@hawaiiyachtgroup.com.